The invention relates, generally, to ink jet printers and, more particularly, to an improved device for drying the ink image.
Ink jet printers are used in a wide variety of printing applications. One such application is the printing of images such as expiration dates and lot numbers on cans, bottles and the like on high speed automated conveyor lines. Typically, the cans or bottles are filled with product, capped and labelled. The labelling process includes the application of the ink jet images directly to the cans and bottles and/or the labelling therefor. Because the ink jet imaging process occurs as part of the high speed operation, it must be carried out rapidly and efficiently where the images are applied and dried for further handling in a matter of seconds.
The ink jet printers used in these high speed applications typically include an ink jet nozzle having an orifice providing a stream of ink. A piezoelectric device surrounds and acts upon the nozzle to cause the formation of drops as the ink leaves the nozzle orifice. The drops are selectively charged by a charging electrode and pass through a deflection field. The deflection field is created by opposed upper and lower electrodes where one electrode is connected to a power supply and the other electrode is grounded or connected to a power supply of opposite polarity. The deflection field deflects selected drops to cause them to strike the substrate being marked, i.e. the can or bottle, to create a desired image. The drops that are not deflected to the substrate are caught by an ink catcher that returns the drops to the ink system for reuse. Typical ink jet printers are disclosed in U.S. Pat. No. 4,845,512 issued to Arway and U.S. Pat. No. 5,196,860 issued to Pickell et al.
As will be apparent, the ink drops applied to the can, bottle or paper will be wet immediately after application. Because ink jet printers are used in high speed applications the wet ink presents handling problems in that the wet ink can be easily smeared or smudged. Thus, it is desired to dry the ink drops after the can, bottle or paper has left the printer.
Known driers typically consist of a heating element and blower positioned downstream of the printing station. The blower forces air over the heating element and onto the newly printed image. The blowers used in this process typically move the air at low pressure and high volume, i.e. on the order of 100-200 cubic feet per minute, to transfer heat to the printed image by convection and/or radiation.
This process utilizes a large amount of air and electrical energy and is relatively inefficient and slow. As a result, the operating cost of the drier is high. Because a large volume of hot air is used, the metal components found in the production line are exposed to the heated air and become extremely hot resulting in a safety hazard. Moreover, if the line stops for any reason the stationary product in front of the heater radiating heat is heated to a level that could damage the product or in the case of paper could start a fire. Finally, the blowers used in this process are large and noisy.
Thus, a safer, less expensive and more efficient ink jet image drier is desired.